WASHINGTON - There was a glimmer in Bryce Harper's eye, a half-smile, perhaps, on his face. It was the ninth inning. The game was on the line. A nasty closer was on the mound.

And Harper, playing for the Washington Nationals in his second big-league game, seemed to be enjoying every second of it.

Last week, Harper, at 19, joined an elite group of players to reach the major leagues at a startlingly young age. With expectations ranging from All-Star caliber to Hall of Fame potential, he isn't unlike Miguel Cabrera and Ken Griffey Jr., Alex Rodriguez and Jason Heyward.

And he isn't unlike Diamondbacks right-fielder Justin Upton.

All of Harper's upper-crust predecessors arrived in the big leagues quickly. Most struggled to some degree. They all fit into the class of player for whom the minor leagues was just a pit stop.

"I don't think there's anything wrong with learning your craft at the minor league level," Nationals General Manager Mike Rizzo said. "I think that's the place to be developed and to learn your craft. Guys with their ability levels often expedite that learning curve because they're so darn talented."

Both Harper and Upton were No. 1 overall picks, Upton in 2005, Harper in 2010. Both changed positions upon entering pro ball, Upton originally a shortstop, Harper a catcher. And both broke into the big leagues as 19-year-olds when an injury opened the door.

Upton came up to stay. Harper, so far, appears likely to do the same.

Upton had an eventful summer at age 19 in 2007. He started the year with High-A Visalia, where he tore apart the California League, hitting .341 in 32 games. The Diamondbacks moved him to Double-A. He kept hitting.

In July, he created more buzz at the Futures Game in San Francisco, getting scouts talking after his rounds of batting practice and then homering in the game.

When Carlos Quentin went down with a hamstring injury in early August, Upton got the call. He remembers being surprised.

"They said to keep playing well and you might get your chance," Upton said. "I was prepared mentally for September. Not necessarily August when I did."

Josh Byrnes, the Diamondbacks' GM at the time, said he had gone to Mobile (Ala.) to see Upton play and visit with him not long before the promotion.

"He was doing well," Byrnes said. "And we needed offense."

With Upton having lived through the ups and downs of his older brother, B.J., himself a teenager in the majors with Tampa Bay, Byrnes thought that could help ease the transition.

Upton's arrival had its ups and downs. At Dodger Stadium, he committed errors in back-to-back innings of his third game. Three days later, he fell a single short of hitting for the cycle against the Pittsburgh Pirates. He then struggled for much of the rest of the season before playing well in the postseason.

"It never goes as you expect it," Byrnes said. "Hanley Ramirez didn't have a very good year in Double-A, was traded and the next year was tearing up the National League. Sometimes it's hard to predict when the talent will translate in the big leagues."

It translated right away for Atlanta's Heyward, who went deep in his major-league debut on Opening Day in 2010 and went on to hit 18 homers with an impressive .849 OPS in his age-20 season. Before deciding to bring him up, Braves GM Frank Wren said the team told Heyward in spring training he had a chance to make the team.

"Sometimes it's very easy for a kid to come into big-league camp with no expectations of making the team and perform very well," Wren said. "The first task was to see how he reacted to knowing he had a chance."

But Heyward struggled in his second season. He hurt his shoulder in March, developed bad habits at the plate and never really got on track. Wren wasn't necessarily surprised that Heyward hit a rough stretch early in his career -- "I don't know a player that hasn't, with the exception of maybe Albert Pujols," he said -- but for players of Heyward's caliber, sometimes the majors is the best place to learn.

"The game is faster here," Wren said. "The worst pitcher on a 12-man staff is better than most anybody you'll see down there, with the exception of the bright star coming up. You're tested every at bat and if your game isn't well-rounded, they're going to expose it."

Upton acknowledged this, saying there were things he was able to get away with in the minors that he found out quickly he couldn't do in the majors. But he said the biggest thing he has learned since he was a rookie is in his mental approach.

"I wish I had known to relax and play the game," Upton said. "It's not that there's pressure from an outside source, but you're a competitor and you want to do well. When you're not doing well, you tend to go harder, rather than taking a step back.

"You're competing against other people's words sometimes. The older you get the more you realize that those words actually don't matter. What people are saying doesn't matter. It's all about what you can prepare yourself to do and how successful you can be."

Whether Harper knows these things or still needs to experience it himself to learn them remains to be seen. But in his first week in the majors, one thing seems clear. He's having fun.

"I got really calm when I got (to the majors)," he said. "In Triple-A, it's like I've got to prove because I want to get up there so bad. Now I'm here. Stay in the moment."

Rizzo won't guarantee that Harper, who was added to the team when star third baseman Ryan Zimmerman went on the disabled list, will stay up all summer. Right now, it's hard to imagine him going down.

"His make-up is the brighter the lights the better he plays," Rizzo said.

Notable: Compared to last season, Saunders is striking out more batters per nine innings (5.9 from 4.6) and walking fewer per nine innings (2.3 from 2.8). Through 10 starts, he's thrown 62 1/3 innings, putting him on pace for more than 200 innings. ... Saunders threw pretty well against the Giants at AT&T Park last week, giving up one run in 5 1/3 innings. ... He did not have a great month of May, however, posting a 6.12 ERA in six starts. ... Friedrich was the 25th overall pick in the 2008 draft out of Eastern Kentucky. He has a four-pitch mix, with a curveball, slider and change-up to go with a fastball that averages 91.7 mph, per Fan Graphs. ... He had a 3.00 ERA in 30 innings (four walks, 27 strikeouts) in Triple-A Colorado Springs before being recalled. ... He gave up just two runs in 13 innings in his first two starts, but he has been hit around in his previous three, allowing 16 runs on 27 hits in 16 innings.